This invention relates to a laminate of polyester and plasticized polyvinyl butyral and more particularly to i) such a laminate displaying improved adhesion between the layers, ii) the method of improving such adhesion and iii) the method of forming the laminate.
Plasticized polyvinyl butyral (PVB) is well known as a shock-absorbing interlayer in safety glazings for vehicle, aircraft and architectural window and security (e.g. jewelry casings) applications. Particularly with vehicle windows, additional functional layers are being proposed in such safety glazings to provide features such as solar energy control, weight reduction by eliminating one glass layer (called a bilayer structure), head-up displays in automobiles and liquid crystal and electrochromic devices for privacy applications. The delicate functional layer(s) providing these enhanced features must be deposited on a suitable substrate which cannot be the PVB layer because of its unusually soft, pliant, plasticized nature. However, to provide penetration-resistance in the safety glazing the PVB layer must be included which means that the substrate for the additional functional layer must be joined to the PVB layer before or during lamination with glass. Polyester film such as polyethylene terephthalate stretched in one or two directions has been used as such a substrate since it is widely commercially available, relatively inexpensive and has good clarity and mechanical strength. However, without initial surface modification it does not adhere sufficiently tenaciously to plasticized PVB to preserve the integrity of the safety glazing laminate of which both layers are a part over the intended useful life of the glazing.